A head-up display generates an image on a screen, for example, with a MEMS mirror. The image generated on the screen is emerging as image beams. The image beams are reflected by a reflection mirror etc. called a combiner, then magnified by a magnifying device etc., and finally are guided to the eye position or the eye point of the driver. The image generated on the screen is perceived from the eye point as a virtual image.
There is a conventional technique proposed for a head-up display screen to use a micro lens array, which is composed of a large number of lenses periodically arranged. However, in a case where a sheet of the micro lens array is applied to a screen, the periodic structure of the micro lens array causes diffracted beams, resulting in a problem of luminance unevenness.
Patent Document 1 therefore discloses a technique for using two sheets of micro lens arrays, that is to say a first micro lens array unit and a second micro lens array unit. The two micro lens arrays are oppositely arranged and spaced from each other by a distance longer than the focal distance of the micro lens array disposed in the first micro lens array unit. Also, the intervals between the micro lenses disposed in the first micro lens array unit are configured to be narrower than those in the second micro lens array unit. This prevents excessively bright spots from being generated. Namely, by using the two micro lens arrays, generation of the diffracted beams resulting from the periodic arrangement of the micro lens arrays can be prevented.